"At a moment when she should have been most concerned with her own health," Ohanian told Inc., "she was apologizing to me, because she didn't want that weighing on my conscience while I was trying to do everything else I wanted to do up in Boston, where our company was."

Here are some more details on the creation and sale of Reddit:

Paul Graham, co-founder of Y Combinator, rejected their original idea: a mobile food ordering service called MyMobileMenu. Instead, Graham told them, "You guys need to build the front page of the Internet."

They had a contentious debate about whether to include comments. (They did.)

Within a month of creating Reddit, the mother of Ohanian's then-girlfriend called him with the news that her daughter accidentally fell five stories off a balcony in Germany and was in a coma. The hospital released her a few months later.

Then Ohanian got the phone call from his dad about his mom.

In 2006, Condé Nast approached Ohanian and Huffman with an offer. "Founders are supposed to be not at all interested in selling," Ohanian said. "But there is a price at which a founder can't help being interested." After 16 months of working on Reddit, they sold it for somewhere between $10-20 million.

"To be able to call my mom as soon as the bank account cleared and tell her—before I told TechCrunch—to tell my mother her confidence in me was not wasted was the best part, absolutely the best part," Ohanian said.